There are several methods of locking swivels in position.
These can be split in to two categories; fixed and repositionable.

Fixed Methods

The fixed methods, such as crimps, usually involve a metal tube which needs to be gently squeezed on to the rig body. Too much pressure, or the use of the wrong tool, can result in damage to the line, and thus a weakened and unsafe rig. The other issue is that if a clipped fishing rig is used, such as a cascade rig, and there is a need to replace a hook or snood during a fishing session it will prove almost impossible to tie the snood/hooklength to the correct length to clip perfectly.

However, fishing with rigs that use crimps etc. does offer one huge advantage; they are very compact. This is a particular advantage for the following:

Fishing at extreme range:
Decreases air resistance during the cast.

Fishing in a strong current:
Minimises water resistance making it less likely that they lead will accidentally trip.

Fishing in weedy conditions:
Reduces the opportunity for weed
to build up.

Crimps

Crimps for general beach use are a copper tube tube that will accept line up to around 8olb. The line is passed through the sleeve and then lightly squeezed using crimping pliers. Applying too much pressure will damage the rig body, as can using pliers or other tools which have jaws with ‘teeth’.

Approximate cost: 3p per crimp

Smarties

These are an ‘all-in-one’ system that is in effect the swivel, beads and crimps. They are squeezed on to the rig body just like you would a crimp.

Approximate equivalent cost: 5p per stop
This takes in to account the cost of a swivel and 2 beads.

Repositional Methods

Repositional methods of locking a swivel in place, such as silicon tube stops or powergum stop knots, offer a number of key advantages over fixed methods, with the only real disadvantages being a slightly bulkier rig and some adjustment occasionally being required to keep everything taught when clipped.

Benefits of repositional methods of locking a swivel in place:

Does not weaken rig body

No problems cause by snood/hooklength stretch with clipped rigs

Enables rigs to be reconfigured in seconds

Rig bodies can be re-used and re-tied (if free from damage)

Silicon Tube Stops

These are created by taking a 4-5mm length of high quality 1.5mm silicon tube, passing the rig body line through it twice and pulling tight. As a general guide it takes 3 stops to hold a snood in place, although if a SRT Spring is used on the rig it can take five or six to lock it firmly in position. When silicon tube stops are removed from the line they revert back to a tube and can be used again, which makes them very cost effective.

Approximate cost: less than 1/2p per stop

Powergum Stop Knots

Powergum stop knots are smaller than silicon tube stops but take longer to tie. They grip the rig body much better than silicon tube stops which means that fewer are required to effectively lock a swivel in place, however, they aren’t reusable.

Approximate cost: 3p per knot

Rubber/Silicon Gromits

These come threaded on to a metal wire and require transfering on to the rig body. They are very streamlined which aids in distance casting, but like silicon tube stops a number will be required to lock the swivel in place. The downsides are that they are not easily reusable, and I have experienced the metal wire snapping, preventing them from being transfered to the line.